Role of adrenergic tone in mechanical and functional properties of carotid artery during aging

Abstract

The present study was designed to assess the role of the adrenergic tone in the regulation of carotid arterial compliance during aging. An experimental model of in situ isolated carotid arteries has been used to evaluate the elastic properties of the arterial wall in young (3-mo-old) and older (18-mo-old) Wistar rats. Binding experiments were performed in the same strain of rats to evaluate alpha 1- and beta-adrenoceptor affinity and density. In a third set of experiments, structural parameter of the carotid artery in younger and older rats was evaluated. Arterial distensibility (compliance per unit of volume) was significantly lower in older rats. This was associated with a significant thickness of the media (45.6 +/- 2.8 vs. 57.5 +/- 5.7 microns, P < 0.01) and increased collagen content in older rats (4,420 +/- 310 vs. 7,320 +/- 850 microns 2/mm, P < 0.001). However, carotid arterial compliance was not altered in older rats because of the significant increase in cross-sectional area with aging. Aging did not affect alpha 1-adrenoceptor affinity and density, whereas it decreased beta-density without changing their affinity. Pharmacological stimulation of alpha 1-adrenoceptor with phenylephrine (10(-5) M) decreased compliance in older but not in younger animals. Blockade of these receptors with prazosin or labetalol increased compliance in younger and had no effect on older rats. beta-receptor stimulation with isoproterenol or blockade with propranolol had no effect in any of the studied groups. We suggest that with aging there is an increased vasoconstricting effect of alpha-agonists and a decreased vasodilatative action of alpha-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

A long-term moderate magnesium-deficient diet aggravates cardiovascular risks associated with aging and increases mortality in rats

“…Our results are in agreement with those of clinical and experimental studies: the arterial wall progressively thickens and becomes stiffer with age [17][18][19][20]. The present study confirms an increase in collagen content in the arterial wall of aorta of old rats [15].…”

Age-Related Disappearance of the Inhibitory Effect of Vascular Endothelium on Agonist-Induced Vasoconstriction in Rat Mesenteric Vascular Beds

“…Therefore, it is unlikely that the time-dependent reduction in methoxamine-induced tonic vasoconstriction in 8-week-old preparations is due to decreased constrictive activity of arterial smooth muscles. Some studies have shown no age-dependent changes in the density of α 1 -adrenoceptors (22,23). Furthermore, high KCl-induced vasoconstriction was not altered with aging, suggesting that membrane depolarization-induced smooth muscle contractility is not responsible for the age-related disappearance of the time-dependent reduction in methoxamine-induced vasoconstriction.…”

Hemodynamics and Arterial Properties in Response to Mental Stress in Individuals with Mild Hypertension

“…Pharmacologically induced increases in adrenergic tone have been shown to decrease distensibility of in situ isolated carotid arteries in rats (3). Conversely, carotid and femoral arterial distensibility increased and elastic modulus (ie, stiffness) decreased in sympathectomized rats (4).…”